HEI dizzy is an easy fitment. Just leave your leads and cap where they are. Get a HEI dizzy from a VC-VL or WB 5 litre or VC-VH or WB 4.2L and put it in. Use an XD-XE rotor button and put the cap back on. Fit an XD-XE coil. Bridge the start and run wires at the ignition switch (pink and yellow from memory) and you are away. If the dizzy is an unknown qualtity get it overhauled with a new module and new vacuum advance mchanism. Dr Terry at Bebco in Sydney overhauls these.